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多金属结核比表面积分析测试条件研究

Studies on Analysis Conditions of Specific Surface Area of Polymetallic Nodules

  • 摘要: 多金属结核富含多种关键战略金属,是重要的深海沉积矿产。多金属结核疏松多孔,具有从海水/孔隙水中吸附痕量金属进而富集成矿的关键材料学特性,其比表面积是成矿作用研究的一个关键参数。目前比表面积测试技术方法成熟,但很少应用于多金属结核的比表面积分析,且由于研究目的不同,样品预处理条件也不同。本文探究了多金属结核BET比表面积测试的预处理条件,为多金属结核富集痕量金属研究提供必要参数。对取自西太平洋、印度洋和大西洋的多金属结核样品,基于低温氮吸附法与静态容量法,采用程序升温、累积加热和粒度对比三种实验技术路线,对多金属结核比表面积分析的预处理温度、时间和试样粒度条件进行了研究。结果表明,程序升温测试在加热到210℃时比表面积测试结果进入平台期,一直持续到350℃;在210℃条件下,以1h为梯度累积加热测试比表面积,样品在累计加热3h后测试结果基本稳定。毫米级的块状试样相较微米级的粉末状试样,其比表面积测试值偏高1.027~28.535m2/g。研究认为,选取毫米级精度的块状样品在真空状态下210℃加热3h,比表面积测试所得数据能够代表多金属结核的稳定测试结果。该成果为多金属结核成矿作用研究提供了比表面积分析的预处理条件。

     

    Abstract:
    BACKGROUNDPolymetallic nodules are predominant in deep sea sedimentary mineral resources due to the enrichment of many critical metals. Polymetallic nodules are loose and porous, which is the critical material feature that contributes the adsorption of trace metals from seawater and pore water and then enrichment and mineralization. Therefore, specific surface area (SSA) is one of the key factors for studying the ore-forming process of polymetallic nodules. At present, the methods for SSA determination are well-developed. However, they are less applied in the analysis of the specific surface of polymetallic nodules, and the pretreatment conditions are not constant according to various research targets.
    OBJECTIVESIn order to explore the pretreatment conditions for the BET SSA analysis of polymetallic nodules, and provide necessary parameters for the study of the enrichment of trace metals in polymetallic nodules.
    METHODSPolymetallic nodules from the Atlantic, Indian, and Pacific oceans were collected. The pretreatment conditions including temperature, duration, and particle size for SSA analysis of polymetallic nodules were studies by applying temperature programming, heating accumulation, and particle size comparing methods.
    RESULTSThe results showed that the analysis values of SSA reached plateau when the heating temperature ranged from 210℃to 350℃. The analysis values of SSA remained constant after heating for 3 hours by a step of 1 hour at 210℃. The SSA values of samples with a size of several millimeters were 1.027-28.535m2/g higher compared with those of the same samples crushed into microns.
    CONCLUSIONSReliable SSA values can be obtained when the polymetallic nodules with sizes of several millimeters are heated in a vacuum system for 3 hours at 210℃, which is the pretreatment condition for analyzing SSA of mineralization-related polymetallic nodules.

     

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